Map data for electronic navigation devices, such as GPS based personal navigation devices like the GO™ from TomTom International BV, comes from specialist map vendors such as Tele Atlas NV. This map data is specially designed to be used by route guidance algorithms, typically using location data from the GPS system. For example, roads can be described as lines—i.e. vectors (e.g. start point, end point, direction for a road, with an entire road being made up of many hundreds of such sections, each uniquely defined by start point/end point direction parameters). A map is then a set of such road vectors, data associated with each vector (speed limit; travel direction etc.) plus points of interest (POIs), plus road names, plus other geographic features like park boundaries, river boundaries etc, all of which are defined in terms of vectors. All map features (e.g. road vectors, POIs etc.) are typically defined in a co-ordinate system that corresponds with or relates to the GPS co-ordinate system, enabling a device's position as determined through a GPS system to be located onto the relevant road shown in a map and for an optimal route to be planned to a destination.
To construct this map database, Tele Atlas starts with basic road information from various sources, such as the Ordnance Survey for roads in England. It also has a large, dedicated team of vehicles driving on roads, plus personnel checking other maps and aerial photographs, to update and check its data. This data constitutes the core of the Tele Atlas map database. This map database is being continuously enhanced with geo-referenced data. It is then checked and published four times a year to device manufacturers like TomTom.
Despite the huge resources that go into updating and verifying these maps, the data for some geographic areas may be a year or more out of date.
In addition to the ongoing improvements described above, end-users can directly report map errors to Tele Atlas using Tele Atlas' web site. Device manufacturers like TomTom also capture and forward map error reports from their users in this way. These error reports are generally just in a free text format, so that considerable effort has to be expended in working out what the error really means and what exact location they relate to. Once verified as a real error, the appropriate correction is validated and then included in a future map release. The correction may eventually find itself in an end-user device a year or more after first being notified or, in some cases, not at all.
It is also known to store a ‘trace’ of a journey planned and completed using a GPS satellite navigation device (see for example the ‘GPS track submission’ functionality offered by ALK Technologies of Princeton, USA). This trace is a record of the complete route taken by a vehicle, using geo-coded data. The user can then send this trace data back to the device vendor; it is then used to improve the accuracy and completeness of the map database. For example, the precise position of a road or a turning may not be accurately captured on a map used by a device; the aggregated tracks for people taking that road or turning will enable a more accurate position to be determined; future map releases by the device vendor can incorporate the correction.
Reference may also be made to collaborative mapping projects, frequently called ‘wikimaps’. Wikimaps do not however generate ‘map data’ as we define that term—i.e. map data that is suitable for route guidance algorithms to plot a route on a road system to a destination.